The use of energy-absorbing components for the protection of the vehicle frame in a frontal collision is commonly known. In most cases, the protection is provided by a side rail protection component between the front ends of the two side rails of a vehicle's frame and the front cross member.
Such vehicle frame protection components are not to be confused with the component widely known as the bumper of a vehicle. A vehicle's bumper is generally placed in front of the front cross member of the frame. With newer vehicle models, the bumper consists mainly of easily deformable plastic parts which enhance the vehicle's exterior design. However, bumpers are often strengthened mechanically by placing additional plastic parts or energy-absorbing PU foam parts in the cavity between the bumper and the front cross member of the frame. Older models in particular often use bumpers made of steel sheet, aluminum-strengthened steel sheet or similar materials, which are connected to the vehicle frame via flexible hydraulic components, so that the hydraulic components deflect impact collisions which occur at lowest speeds from the frame. Commonly used bumper designs can be found in the automobile engineering handbook by Robert Bosch GmbH, 22nd edition, Stuttgart, 1995 on page 686. While the commonly marketed vehicle frame protection components have the purpose of preventing permanent damage to the vehicle frame at higher speeds, such as speeds from 5 to 25 km/h (approx. 3 to 15 miles/h), bumpers only serve to protect the rigid vehicle frame from deformations caused by impact collisions at speeds up to 5 km/h (approx. 3 miles/h). The bumper absorbs most of the impact energy, so that the vehicle's frame is only damaged by much stronger impact forces caused by a collision.
Deformed vehicle frame protection components can easily be exchanged with new components. This makes expensive repairs of frame damages after a collision at moderate speed unnecessary by simply replacing one or several vehicle frame protection devices, considerably reducing repair costs. This is one of the reasons insurers insist on repeated or regular functionality checks of such vehicle frame protection components especially with newly registered cars, before all vehicles of identical design are classified within the same damage class.
The automobile industry has long added pressure and acceleration sensors to different points of a vehicle. These sensors plus their electronic parts (which evaluate the signals) are mostly used as crash sensors, often also as so-called early crash sensors. Early crash sensors emit their signals to a passenger protection system's central controller which uses the data to determine the severity of the accident. Based on the severity determined, a passenger protection device is triggered (sometimes modified) when an additional crash sensor or central controller sensor signal provides sufficient cause to trigger the passenger protection device. For example, an airbag is inflated to the first or second inflation level according to the severity of the accident.
From the German patent disclosure DE 196 02 990 A1 it is also known to determine a vehicle's impact collision from the increase in pressure in a cavity behind a bumper using a pressure sensor. Depending on the pressure sensor data, a passenger protection device is then triggered, such as an airbag, a belt tightening device or similar devices.
German patent registration DE 103 31 862.3 furthermore presents a vehicle protection frame element which is deformed permanently and the cavity of which is equipped with a pressure sensor to measure an increase in pressure during a collision. From the pressure signal, a central controller determines the severity of the collision and triggers the suitable passenger protection device according to need.
Furthermore, the German patent registration DE 103 32 377.5 involves a hydraulic bridging element for bridging the gap between the engine/drive block and a cross member. The forces impacting the vehicle during a collision are used to push the fluid from the fluid reservoir into the hydraulic bridging element. The inserted fluid extends or elongates the hydraulic bridging element in order to bridge the gap between the two components. In this way, additional force paths are created which slow down collision-driven movements of heavy components like the engine/drive block and provide for geometric compatibility in order to protect and relieve the passenger cabin. On the other hand, part of the impact energy can be redirected in order to support the components against the introduced collision forces and against other parts of the vehicle.